1. Field of the Invention
This invention relates to a "free" pumping apparatus safety valve system. More specifically, it is directed to an improved, free pumping apparatus safety valve system for use in producing a formation fluid that provides a safety valve and a recirculation valve.
Presently, the need for natural gas and oil is increasing without a proportionate rise in price. Therefore, to remain competitive, companies must continuously become more efficient in their recovery of these resources.
In general, a well includes a well casing that is perforated within the formation. The well casing has a longitudinal passageway that provides flow communication with the surface for recovery of formation fluids. Other possible well configurations include a well tubing mounted within a well casing wherein the well tubing provides the flow communication to the surface. In addition, the well tubing may extend below the well casing in an open hole configuration. Because of the prolificacy of well configurations, the well casing and, if applicable, well tubing are hereinafter referred to generally as a well bore fluid communication conduit.
A number of pumps are used to aid recovery of the formation fluids. Devices proven to provide efficient recovery of formation fluids, such as natural gas and oil, are downhole jet pumps and downhole reciprocating pumps. These downhole pumps are mounted in the bottom of the well bore fluid communication conduit below the formation fluid level. A hollow tubing, either conventional tubing or coil tubing, within the well bore fluid communication conduit provides fluid communication between the surface and the pump's power fluid inlet.
Certain of these pumps are "free," or capable of recirculation from the bottom of the tubing. A free pump is made of two separate main parts. The first part is the housing which is fixedly mounted to the lower end of the tubing. The second part is the pump body which has a small diameter and contains a number of the pump parts that are typically subject to wear or blockage. When the pump body is inserted in an upper end of the tubing and a power fluid is then transmitted therethrough, the pump body's compact design permits it to travel through the tubing to the tubing's lower end. The housing is designed to slidably, removably, and operatively receive the pump body. Once in the housing, the pump body and housing form the jet pump which may then commence operation.
To provide for low cost maintenance of the pump body parts, removal of the pump body is easily accomplished by reversing the flow through the system, or pumping fluid downwardly through the well bore fluid communication conduit and receiving it upwardly through the tubing. In this way, the pump body slides from the housing and up through the tubing.
Present pump bodies, however, have power fluid inlets that remain open even during recirculation of the pump body out of the tubing. Thus, the recirculating fluid has a relatively small area on which to force the pump body upward and a substantial amount of the recirculated fluid simply flows through the pump body. Consequently, the energy required to recirculate the fluid that simply passes through the power fluid inlet is wasted. Also, because power fluid inlets remain open during recirculation, the pump body is relatively less responsive to recirculated flow than if the power fluid inlets were closed.
A great proportion of the producing natural gas and oil reserves are located offshore. To protect the sensitive oceanic environment, offshore oil wells must meet strict environmental and safety regulatory requirements. One such requirement, is that the well provide a safety valve so that, in the event of damage to the well bore fluid communication conduit, and subsequent loss of power fluid pressure, formation pressure will not force formation fluids into the ocean and, thereby, cause environmental harm. Currently, free pumps do not meet this requirement and cannot be used in offshore wells. Once positioned in the pump housing, the pressure supplied by the power fluid maintains the pump body in the pump housing. In high volume producing formations, the formation fluid is under pressure and, thus, exerts an upward force on the pump body. Consequently, the downward pressure supplied by the power fluid must be greater than the upward force of the formation fluid. When the well bore fluid communication conduit or the tubing is damaged, the power fluid cannot supply the downward pressure required to maintain the pump body in the pump housing. Thus, the formation fluid forces the pump body from the pump housing. Depending upon the amount of pressure supplied by the formation and the location of the damage to the well bore fluid communication conduit, the formation fluid may escape from the well bore fluid communication conduit.
2. Related Art
Free pumps and other formation fluid recovery devices have long been known to the prior art. Illustrative of such devices are U.S. Pat. Nos. 1,355,606; 1,758,376; 2,287,076; 2,826,994; 3,215,087; 3,887,008; 4,183,722; 4,293,283; 4,390,061; 4,603,735; 4,790,376; and 4,083,609.
None of the above mentioned references disclose a free pump that provides a safety valve system that stops flow from the well formation to the well bore fluid communication conduit and tubing when the flow of power fluid is interrupted. Nor do these references disclose a check valve within the pump body to provide for more responsive and more efficient pump body removal.